How to ignore naming index in modifiers?
There are (at least) two ways to approach this, either you can differentiate the modifiers through their name or their type. 

Filter by Prefix

If you want to filter them by a prefix you could use the following approach to retrieve references to the modifiers. 

First, get the modifier collection of the object. All (key, value) pairs can be accessed through the .items() function. The keys are the names of the modifiers, therefore these have to be checked for a prefix match. Python has the .startswith() function to check if a string starts with a given prefix. If a match is found for a key, the corresponding value is one of the modifiers you're searching for. All of this can be combined to a list comprehension as shown below.

import bpy


prefix = "Subdiv"
modifier_collection = bpy.context.object.modifiers 
modifier_matches = [modifier for key, modifier in modifier_collection.items() if key.startswith(prefix)]

print(modifier_matches)




Filter by Type

Sometimes you may not know the name of the modifiers, since these are user editable, but you may know their type. Searching for modifiers by their type can be accomplished by getting all modifiers of the object through .values() and then checking if they are of a certain type, e.g. SUBSURF in the example below.

import bpy


modifiers = bpy.context.object.modifiers.values()
modifier_matches = [modifier for modifier in modifiers if modifier.type == "SUBSURF"]

print(modifier_matches)




The example below shows how to iterate through all modifiers of an object, check if its name starts with a given prefix and if it does, disable it for rendering by setting show_render to False.

import bpy


for key, modifier in bpy.context.object.modifiers.items():
    if key.startswith("Subdiv"):
        modifier.show_render = False